Magic Potions
Magic potions are liquid-based magical solutions that are normally imbibed to gain the effect upon yourself, but in some cases are poured onto a weapon, or even a patch of ground. In no cases are potions thrown, nor can they ever effect more than one target, even if the spell effect that the potion is enchanted with would normally affect multiple targets. Potions may only be given to willing (or helpless) targets if they are used on someone other than yourself.
Drinking a potion is normally a standard action, and that assumes the potion is in a location where it is readily available, such as in a belt pouch, or on a bandoleer. If it is in such an easily accessible location, drawing the potion is part of the same standard action as drinking the potion. If it is in a less accessible location, the potion must first be drawn into one's hand before it can be consumed.
While you must, technically, have a hand free to draw a potion and pour it into your mouth, a number of weapons and wielded objects leave enough room in your hand to also hold a potion. This includes all light weapons, light shields, bucklers, rods, and wands. Two-handed weapons can be held in one hand while the other releases the weapon (a free action) to draw the potion. As a result, in most cases, the GM and players don't really need to worry about the 'need a hand free' requirement, unless the character attempting to draw the potion is obviously unable to let go of anything they're currently wielding or carrying with either of their hands.
For those interested in drinking potions often, the Quick Draw feat, the Quaff feat, and the Sipping Jacket all help make the act of drawing and drinking a potion much easier.
Note that some potions, such as Feather Fall, are only an Immediate Action to cast, but are still a standard action to drink as a potion. This significantly diminishes the usefulness of these potions unless you have some means of drinking potions more quickly.
Potions are stored in crystal vials, and are usually about 3 ounces of liquid, making them easy to consume quickly, even if you aren't particularly thirsty. Of course, potions rarely taste good, and some have been known to taste like impossible things, such as 'the color red', or 'a very itchy rash'. Magic is funny that way, and drinking magic isn't for the faint of heart.
The crystal vials are unusual in that they are quite durable. They will not break if dropped, or even if thrown. They can, however, be Sundered, even without a weapon that has the Sunder quality (since they are not made of, or reinforced with, metal or stone). Any sunder damage or siege damage that would deal 1 point of durability damage to a potion will smash the vial and destroy both it and its contents. Potion vials destroyed in this way cannot be repaired, even with Greater Make Whole or similar magic. They are destroyed and not recoverable. Best protect your potions.
Only spell effects as high as spell level 4 can be made into potions, and even then, only a few spells are available in potion form. The table below contains a list of every potion that has ever been successfully crafted by a skilled creator. (GMs may allow spells other than those on this list to be made into potions on a case-by-case basis, but probably shouldn't. If a spell isn't on this list, there's a reason for it. Most often, it is because the spell effect requires a non-willing target, but in some cases, such as Mage Armor, the spell was left off this list because it is an ability reserved only for those who practice that type of magic and cannot be shared out to the rabble in a simple drinkable form.)
List of Available Potions
Magic Potion Costs
Magic potions have a cost based on the creator level of the potion. Most potions are brewed at the minimum creator level required for the spell effect the potion will convey ((2 * spell level) - 1), but it is possible to purchase a potion with a higher creator level than the minimum.
All effects of the potion are resolved against this creator level. The drinker's character or caster level, ability scores, class features, feats, etc. are all ignored; only the potion's creator level is used to determine the specific effects of the potion on the drinker.